Conventional integrated circuit (IC) devices may contain one or more dies and/or packages arranged in stacks. Components in such stacks may be electrically coupled using solder balls or bumps, and an underfill material may be provided to fill the space between the components and surround the solder balls or bumps. During operation, various regions of the dies and/or packages may generate significant amounts of heat. These regions may be internal to the IC device, and therefore the heat generated in these regions may not be adequately managed using traditional external heatsinks. Additionally, the location of the hottest regions may change over time as the IC device operates in different modes.